Electrical resistor



y 29, 1956 M. w. CRAINE 2,748,233

ELECTRICAL RESISTOR Filed Fgb. 20, 1952 INVENTOR. m MARVIN l V. CeA/NE ATTOENEKS United States Patent ELECTRICAL RESISTOR Marvin W. Craine, Dexter, Mich., assignor, by inesne assignments, to Simon A. Bahr, New Brunswick, N. J.

Application February 20, 1952, Serial No. 272,581

9 Claims. (Cl. 201-67) This invention relates to an electrical resistor and the method of making the same.

It is an object of this invention to provide an electrical resistor adapted to dissipate heat rapidly so that the resistor does not become overheated.

A further object of the invention resides in the pro vision of a method by which a resistor of the above type may be manufactured economically.

in the drawings:

Fig. 1 is a perspective view of the resistor of this invention mounted on an electrical conducting supporting member.

Fig. 2 is a plan view of the blank from which the shell of the resistor is formed.

Fig. 3 is a top plan view of the shell of the resistor after the first forming operation on the blank shown in Fig. 2.

Fig. 4 is a sectional view along the lines 4-4 in Fig. 3.

Fig. 5 .is a view similar to Fig. 3, partly in section, and showing the shell after the necessary holes have been pierced therein.

Fig. 6 shows a resistor in the form of a wire coil arranged within the shell shown in Fig. 5.

Fig. 7 is a bottom plan view of the shell in the semiclosed condition with the resistor coil arranged therein.

Fig. 8 is a view in side elevation of the assembly shown in Fig. 7.

Figs. 9 and 10 are bottom plan and side elevation views, respectively, of the resistor assembly after the final closing operation.

The resistor of this invention generally includes a metallic shell 10 and an electrical resistor in the form of a wire coil 11. The shell 10 is formed from a blank 12 which is generally circular in shape. Blank 12 is formed from sheet metal, preferably a metal, such as aluminum, brass or copper, which provides good heat and electrical conductivity. Around .its outer edges, blank 12 is scalloped to form a series of tabs 13 spaced apart by V-shaped notches 14. The radial and circumferential extent of the tabs 13 and notches 14 are predetermined as will be more fully explained hereinafter.

in forming the blank 12 into the shell 10, the first operation comprises the step of stamping the blank into the partially formed shell 15 illustrated in Fig. 4. This can be performed by means of suitable stamping dies as will be readily understood. The partially formed shell 15 has a fiat central portion 16 around which extends a depending annular trough 17, the trough 17 having substantially parallel inner and outer circumferential walls 18 and 19. The tabs 13 extend upwardly from the outer side Wall 19 and project above the plane of the fiat central portion 16. The apices 20 of the V-shaped notches 14 are aligned generally in the plane of the central flat portion 16. The partially formed blank 15 is thereafter provided with a central aperture 21 in the portion 16 and a second aperture 22 in the outer side wall 19. Aperture Patented May 29, 1956 22 is generally horizontally aligned with the plane of central portion 16.

The coil 11 is formed of a piece of insulation-covered resistance wire of predetermined length, the diameter of the coil corresponding generally to the diameter of trough 17 so that coil 11 may be curved axially into arcuate shape and arrangd within trough 17 with the walls of the trough 1'7 embracing the coil and in heat-conducting relation therewith as is best shown in Fig. 6. One end 23 of coil 11 is provided with a sleeve 24 formed of an insulating material such as fiber glass and is extended through the opening 22 in the side wall 19 of trough 17. The other end 25 of coil 11 is extended out of trough 17 over the face of central portion 16 and the bored end portion 26 thereof is booked through and around the edge of central opening 21. After coil 11 is thus arranged within trough 17 of shell 15, the assembly is in condition for closing the open face of trough 17. This is accomplished by bending or folding tabs 13 inwardly .into the plane of the central disc portion 16.

In Figs. 7 and 8 the shell is shown in the semi-closed condition, and in Figs. 9 and 10 the shell is illustrated in its fully closed, completely finished condition. It will be observed that the notches 14 around the edge of blank 12 provide the necessary clearance between the successive tabs 13 to permit the tabs to be folded into the plane of the disc portion 16 to completely close the open face of trough 17 without overlapping the adjacent edges of the tabs. in other words, the one face 27 of the completely assembled resistor is substantially fiat and comprises the folded-over tabs 13 and the central disc portion 16.

It is desirable to form the resistor with the flat face 27 so that it may be mounted on a support such as a fiat terminal 28 with the face 27 providing a wide area of contact between the shell 11) and the terminal. Thus, the heat produced by the current flowing through coil 11 is quickly absorbed by the shell 10, and this heat is readily conducted by means of the flat face 27 of the shell to the terminal 28 or other member on which the resistor is mounted. The central aperture 21 enables the resistor to be readily mounted on a support by means of a screw 29 passing through aperture 21 and a corresponding aperture in the support. The same screw 29, by means of which the resistor is mounted on the support 28, serves to hold the hooked end portion 26 of the coil in electrical contact with the terminal 28.

I claim:

1. A resistor comprising a length of insulated wire wound into a resistance coil and fashioned into generally circular shape, a sheet metal shell supporting and substantially completely enclosing said coil, said shell having a tubular portion of ring shape which snugly encloses and embraces said coil, and a flat central disc portion surrounded by said tubular portion, said disc portion being joined integrally with said tubular portion.

2. A resistor comprising a sheet metal shell having a flat central portion and a scalloped peripheral edge portion, said scalloped edge portion being fashioned to provide a substantially closed tubular chamber extending circumferentially around said central portion, and a resistance coil of insulating Wire enclosed within said tubular chamber and in heat-conducting relation with and embraced by the walls thereof.

3. A resistor comprising a sheet metal blank having a flat central portion and an annular trough extending around said central portion, a resistance coil of insulated wire disposed within said trough, the free edge portion of said trough being scalloped, said scalloped edge portion being bent inwardly over said coil into the plane of 3 said flat central portion such that the coil is substantially completely enclosed by said trough.

4. The method of making an electrical resistor adapted to dissipate heat readily which comprises providing a generally ilat, circular sheet metal blank, bending the circumferential edge portion only of the blanl:v to form an annular receptacle upon the one face thereof which extends circumferentially around a flat central portion of the blank, arranging within said receptacle a coil of resistance wire such that the coil extends generally as a ring circumferentially around the central portion of said blank, and thereafter bending the extreme edge portion of the blank toward said central portion to close the open face of said receptacle and thereby enclose said coil in heat-conducting relation with said blank.

5. The method according to claim 4 including the steps of forming an aperture .in a side wall of said receptacle and extending one end of said coil through said aperture.

6. The method according to claim 4 wherein said circumferential edge portion is bent to form a receptacle in the form of a U-shaped channel.

7. The method according to claim 6 wherein said U- shaped channel .is formed with an outer side wall substantially perpendicular to the plane of the central portion of the blank.

8. The method according to claim 7 wherein the channel is formed with an inner side wall, the outer side wall having a greater axial extent in a direction normal to the plane of the central portion of the blank than the inner side wall, the free edge portion of said outer side wall being bent inwardly into the plane of said flat central portion. 1

9. The combination set forth in claim 1 wherein said shell is formed of amaterial which conducts heat readily, the central disc portion of said shell being provided with an aperture therethrough, one end of said coil extending through said central aperture in contacting relation with said central disc portion and the other end of said coil extending outwardly of said tubularportion and being insulated therefrom.

References Cited in the file of this patent UNITED STATES PATENTS Re. 21,232 Van Dyke Oct. 10, 1939 1,997,258 Krieger Apr. 9, 1935 2,158,600 Wiegand May 16, 1939 FOREIGN PATENTS 920,761 France Jan. 4, 1947 

